Habitat preference in Spermophilus major and S-suslicus in recently developed sympatric zone

Since 1995 to 1997, the habitat preference in the spotted and russet sousliks was studied in a sympatric zone developed recently (Ul'yanovsk oblast). Ninety-one pure animal colonies and two contact ones were inspected. For six model colonies, the topography of burrows and gradients by eight environmental factors, including composition of plant cenoses, coverage of the plant cover, and tuff thickness, were taken into account. The Sperman's vauked correlation coefficients were calculated for analyzing the data obtained. The russet souslik, S. major, is shown to prefer xerophytic habitats, the spotted sauslik, S. suslicus, mesophytic ones. Mixed colonies appear in suboptimal habitats; in these colonies, the rate of interspecies competition is low.